Field of the Invention
This invention relates to lasers and fiber optics, and more particularly, to fiber optic collimators.
Brief Description of Related Art
Precision collimation of fiber optic output is critical in many fiber-to-free-space applications throughout industry and academia, for example, in optically-pumped solid-state laser applications. Fiber optic collimators are also regularly used in free-space laser communications.
Solid-state laser performance is highly dependent on a variety of factors pertaining to the pump source such as spot size, waist location, and beam quality. Managing these parameters and being able to tune them in order to optimize laser performance at high-power levels can be a difficult engineering task.
Currently available adjustable collimators address some, but not all, of the following aspects in a single device: wide operational spectral range, wide range of divergence adjustment, industry compatible fiber optic connector types, beam quality preservation, and precision adjustment resolution. In particular, most commercial collimators have a fixed distance between the fiber and the lens and a limited, inflexible focal length.
Variable focus fiber optic collimators do exist, but each of them has its limitations. Some collimators, for example, are designed with a particular integrated lens, which makes the entire collimator assembly useful only for a specific wavelength and/or a very limited focal length/range adjustment.
Another common limitation of commercial collimators is that the lens rotates when the focus is adjusted. This can sometimes add aberration and/or angular pointing of the beam during adjustment if the optical axis of the lens is not perfectly collinear with the mechanical axis of the collimator assembly.
Some commercially available collimators, which are supposedly designed for the popular FC/APC connector, do not address the angle inherent in the connector design. Because of the short distance between the fiber tip and the lens, the offset created by the FC/APC angle is sometimes considered negligible and as a result the beam does not travel through the lens perfectly on axis. This induces two types of beam aberration known as astigmatism and coma. In applications that require good beam quality, this may be unacceptable.